JP2011176288A - Photoelectric conversion element, thin film solar cell, and method of manufacturing photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a photoelectric conversion element that is provided with a stress-relieving layer on an insulating layer to suppress peeling of a layer constituting the photoelectric conversion element; a thin film solar cell; and a method of manufacturing the photoelectric conversion element. <P>SOLUTION: The photoelectric conversion element includes a metallic substrate formed by uniting at least one layer of a metallic base and an Al base, a substrate with an insulating layer having an electrical insulating layer formed on a surface of the Al base of the metallic substrate, at least one stress-relieving layer formed on the electrical insulating layer, a lower electrode formed on the stress-relieving layer, a photoelectric conversion layer formed on the lower electrode and comprising a compound semiconductor layer, and an upper electrode formed on the photoelectric conversion layer. The electrical insulating layer includes an anodized film of aluminum. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flexible photoelectric conversion element, a thin film solar cell, and a method for manufacturing a photoelectric conversion element, which have excellent withstand voltage characteristics using a substrate with an insulating layer provided with an insulating layer and have high conversion efficiency. It is related with the manufacturing method of the photoelectric conversion element which provided the stress relaxation layer on the top, and suppressed peeling of the layer which comprises a photoelectric conversion element, a thin film solar cell, and a photoelectric conversion element.

Conventionally, in solar cells, Si-based solar cells using bulk single-crystal Si or polycrystalline Si, or thin-film amorphous Si have been the mainstream, but in recent years, research and development of compound semiconductor solar cells that do not depend on Si. Has been made. As a compound semiconductor solar cell, CIS (Cu-In-Se) system or CIGS (Cu-In-Ga-Se) composed of a bulk system such as a GaAs system, an Ib group element, an IIIb group element, and a VIb group element is used. And other thin film systems are known. The CIS system or CIGS system has a high light absorption rate, and high photoelectric conversion efficiency has been reported. In addition, although the film formation temperature of amorphous Si is about 200-300 degreeC, when using a CIGS type compound semiconductor as a photoelectric converting layer, in order to obtain a high performance characteristic, about 520 degreeC in which the liquid layer of Cu-Se appears. It is necessary to expose to the above high temperature. In addition, the CIGS-based photoelectric conversion layer tends to increase in efficiency up to about 600 ° C. as the deposition temperature increases.
Furthermore, when productivity is taken into consideration, high-speed film formation is desired. However, it is preferable that the substrate temperature is high if elements in the film are diffused within a short film formation time.

  On the other hand, glass substrates are mainly used as solar cell substrates, but the use of flexible metal substrates has been studied. A solar cell using a metal substrate may be applicable to a wider range of uses than a glass substrate because of the light weight and flexibility of the substrate. Furthermore, since the metal substrate can withstand high-temperature processes, the photoelectric conversion characteristics are improved, and further improvement in photoelectric conversion efficiency of the solar cell can be expected. However, in the case of using a metal substrate, it is necessary to provide an insulating layer on the surface of the metal substrate so that a short circuit between the substrate and the electrode and photoelectric conversion semiconductor layer formed thereon does not occur. Various metal substrates having an insulating layer on such a surface have been proposed (see Patent Documents 1 to 3).

  Patent Document 1 discloses that an insulating layer is formed by using stainless steel as a solar cell substrate and coating an oxide of Si or Al by a vapor phase method such as a CVD method or a liquid phase method such as a sol-gel method. Has been.

  In Patent Document 2, an anodic oxide film is formed as an insulating layer on an Al substrate by forming an anodic oxide film by anodizing the surface of an Al substrate (aluminum substrate) as a solar cell substrate. The use of a metal substrate with an insulating layer is disclosed. In the anodic oxidation method for forming this anodic oxide film, even when the solar cell substrate is a large-area substrate, an insulating layer having no pinholes and high adhesion can be easily formed over the entire surface.

  In Patent Document 3, an Al layer is provided on an alloy steel plate as a substrate of a photovoltaic device having a conventional amorphous Si layer, and an insulating layer is formed on the surface of this layer by an anodic oxidation method. The use of a metal substrate is disclosed. In Patent Document 3, by providing an alloy steel plate as a base material, the alloy steel plate does not soften even if heated to 200 to 300 ° during the process of depositing amorphous Si and the Al layer softens, such as elastic force. It is disclosed that the mechanical strength of can be maintained.

  Incidentally, it is known that the power generation efficiency of a copper-indium-gallium-selenium (CIGS) solar cell improves when sodium (Na) diffuses into the light absorption layer (photoelectric conversion layer). Conventionally, Na contained in blue glass is diffused into the light absorption layer by using blue glass as a substrate. However, when a metal plate other than blue plate glass is used as the substrate of the solar cell, Na must be supplied separately.

JP 2001-339081 A JP 2000-49372 A JP-A-62-89369

  In a solar cell, when a CIGS compound semiconductor currently under study is used as a photoelectric conversion layer, in order to obtain high-quality photoelectric conversion efficiency, it is necessary that the film forming temperature be higher, and in general, Is preferably 500 ° C. or higher, particularly about 520 ° C. or higher at which a Cu—Se liquid layer appears. Therefore, a substrate having a structure capable of withstanding a high temperature of 500 ° C. or higher, preferably 520 ° C. or higher is required. Also, considering the productivity, it is preferable that the substrate temperature is high.

When a substrate in which an anodized film is formed on an aluminum material is used, when exposed to a high temperature, the thermal expansion coefficient of aluminum (23 × 10 ⁻⁶ / ° C.) and the thermal expansion coefficient of the anodized film are 5 × 10. ^The stress caused by the large thermal expansion coefficient difference of about 18 × 10 ⁻⁶ / ° C. to about ⁻⁶ / ° C. is generated in the anodic oxide film, and it cannot withstand this stress, and the anodic oxide film on the aluminum material is cracked. Occurs. Moreover, in solar cells, it is generally known that, for example, a joint portion between an insulating layer and a back electrode layer or a photoelectric conversion material layer is easily peeled off due to a difference in coefficient of thermal expansion.
As described above, when a substrate having an insulating layer provided on the surface of a metal substrate is used for a solar cell, it is required to withstand high temperatures. The current situation is that there is no substrate that cannot withstand high temperatures, withstands high temperatures required for substrates, and has insulating properties.
In addition, when using metal plates etc. other than a blue plate glass as a board | substrate of a solar cell, in order to supply Na, it is preferable to form a photoelectric converting layer into a film at high temperature.

  An object of the present invention is to eliminate the problems based on the prior art, provide a stress relaxation layer on the insulating layer, and suppress the peeling of the layers constituting the photoelectric conversion element, the thin film solar cell, and the photoelectric conversion element It is in providing the manufacturing method of.

  To achieve the above object, according to a first aspect of the present invention, there is provided a metal substrate in which at least one metal base material and an Al base material are laminated and integrated, and the Al base material of the metal substrate. A substrate with an insulating layer including an electrical insulating layer formed on a surface; at least one stress relaxation layer formed on the electrical insulation layer; a lower electrode formed on the stress relaxation layer; and the lower electrode A photoelectric conversion layer formed on the photoelectric conversion layer and an upper electrode formed on the photoelectric conversion layer, wherein the electrical insulating layer is an anodic oxide film of aluminum. The photoelectric conversion element to provide is provided.

In order to achieve the above object, the second aspect of the present invention includes a step of forming a metal substrate by integrating at least one layer of a metal base material and an Al base material, and the metal Anodizing the Al base material of the substrate to form an electrical insulating layer on the Al base material to obtain a substrate with an insulating layer; and forming a stress relaxation layer on the electrical insulating layer; Forming a lower electrode on the stress relaxation layer, forming a photoelectric conversion layer on the lower electrode at a film forming temperature of 500 ° C. or higher, and forming an upper electrode on the photoelectric conversion layer; It provides the manufacturing method of the photoelectric conversion element characterized by having.
Here, the metal substrate is a laminated plate in which a metal substrate and an Al substrate are laminated and integrated, and the step of obtaining the substrate with an insulating layer includes anodizing the Al substrate, The step of forming an anodic oxide film on the surface of the Al base is preferred.

  In each embodiment of the present invention, the compound semiconductor is preferably at least one compound semiconductor having a chalcopyrite structure, and at least one compound semiconductor comprising a group Ib element, a group IIIb element, and a group VIb element. More preferably, the Ib group element is at least one selected from the group consisting of Cu and Ag, and the IIIb group element is at least selected from the group consisting of Al, Ga, and In. More preferably, the group VIb element is at least one selected from the group consisting of S, Se, and Te.

The stress relaxation layer preferably has a thermal expansion coefficient smaller than that of the photoelectric conversion layer and larger than that of the insulating layer. The stress relaxation layer is preferably made of an oxide.
In the present invention, the stress relaxation layer preferably has a thickness of 10 nm to 400 nm, and more preferably 50 nm to 200 nm.
In the present invention, the metal substrate is preferably a laminated plate in which a metal base and an Al base are integrated by pressure bonding.

Further, the photoelectric conversion layer is preferably divided into a plurality of elements by a plurality of groove portions, and the plurality of elements are electrically connected in series.
Moreover, it is preferable that the said stress relaxation layer contains an alkali metal, and it is preferable that the said stress relaxation layer is comprised with the compound which has a silicon oxide as a main component and contains a sodium oxide.
The stress relaxation layer preferably has a two-layer structure, and the first stress relaxation layer on the substrate side with an insulating layer preferably has a smaller thermal expansion coefficient than the second stress relaxation layer on the first stress relaxation layer. The stress relaxation layer has a two-layer structure, and when the photoelectric conversion layer is composed of a CIGS-based semiconductor compound, the first stress relaxation layer on the substrate side with an insulating layer includes ZrN, AlN, and BN. , Al ₂ O ₃ , or ZrO ₂ , and the second stress relaxation layer thereon is preferably composed of a compound containing silicon oxide as a main component and containing sodium oxide.

The metal substrate is preferably a laminated plate in which a metal substrate and an Al substrate are integrated by pressure bonding.
Further, the metal base material is preferably a steel material, an alloy steel material, a Ti foil or a two-layer base material of a Ti foil and a steel material, and the alloy steel material is made of carbon steel or ferritic stainless steel. Preferably, the difference in thermal expansion coefficient between the metal substrate and the photoelectric conversion layer is preferably less than 3 × 10 ⁻⁶ / ° C., and more preferably less than 1 × 10 ⁻⁶ / ° C.
Further, the metal substrate is made of a laminated plate in which an alloy steel material made of carbon steel or ferritic stainless steel and an Al base material are integrated by pressure bonding, and the lower electrode is made of Mo. The photoelectric conversion layer is preferably a layer mainly composed of at least one compound semiconductor composed of a group Ib element, a group IIIb element, and a group VIb element.
The metal substrate is preferably made of Kovar, and the photoelectric conversion layer is preferably made of a compound semiconductor whose main component is CdTe.
The anodic oxide film preferably has a porous structure.
Moreover, in order to achieve the said objective, the 3rd aspect of this invention provides the thin film solar cell characterized by having the photoelectric conversion element of the said 1st aspect.

According to the present invention, by providing the stress relaxation layer, it is possible to suppress the occurrence of cracks in the electrical insulating layer and the occurrence of peeling based on the electrical insulating layer.
Furthermore, according to the present invention, when the lower electrode, the photoelectric conversion layer, and the upper electrode are formed, even if the temperature is raised to a high temperature of 500 ° C. or higher and then lowered to room temperature, The stress generated by the difference in thermal expansion coefficient can be relaxed by the stress relaxation layer, and peeling of each layer constituting the photoelectric conversion element can be suppressed.

Further, according to the present invention, the insulation includes a metal substrate in which at least one metal base material and an aluminum base material are laminated and integrated, and an electrical insulating layer formed on the surface of the aluminum base material of the metal substrate. By using a substrate with a layer, for example, high insulating properties and high strength can be maintained even after a film forming step at a temperature of 500 ° C. or higher, and a manufacturing process at a high temperature of 500 ° C. or higher is possible. For this reason, a compound semiconductor can be formed as a photoelectric conversion layer at 500 ° C. or higher. Since the compound semiconductor constituting the photoelectric conversion layer can be improved in photoelectric conversion characteristics when formed at a high temperature, thereby producing a photoelectric conversion element having a photoelectric conversion layer with improved photoelectric conversion characteristics. Can do.
In addition, since the manufacturing process can be performed at a high temperature of 500 ° C. or higher, it is possible to eliminate restrictions on handling during manufacturing.

Further, according to the present invention, in particular, when the stress relaxation layer is made of an oxide, the stress relaxation layer also functions as an electrical insulating layer, so that the insulation can be further enhanced. Thereby, the withstand voltage is more excellent.
Further, when the stress relaxation layer is made of a material containing an alkali metal, the stress relaxation layer functions as an alkali metal supply source. Thereby, during the formation of the photoelectric conversion layer, the alkali metal can be diffused into the photoelectric conversion layer, and the photoelectric conversion efficiency can be improved. In this case, although the film-forming process of the photoelectric conversion layer is required to have a higher temperature, the substrate of the present invention has high-temperature resistance, so that an alkali metal can be diffused into the photoelectric conversion layer.

It is typical sectional drawing which shows the thin film solar cell which has a photoelectric conversion element which concerns on embodiment of this invention. (A) is typical sectional drawing which shows the board | substrate used for the thin film solar cell which has a photoelectric conversion element which concerns on embodiment of this invention, (b) has the photoelectric conversion element which concerns on embodiment of this invention. It is typical sectional drawing which shows the other example of the board | substrate used for a thin film solar cell.

Hereinafter, based on preferred embodiments shown in the accompanying drawings, a photoelectric conversion element, a thin-film solar cell, and a method for manufacturing a photoelectric conversion element of the present invention will be described in detail.
First, the board | substrate used for the thin film solar cell which has the photoelectric conversion element of embodiment of this invention is demonstrated.
FIG. 1 is a schematic cross-sectional view showing a thin-film solar cell having a photoelectric conversion element according to an embodiment of the present invention.

  A thin film solar cell 30 of this embodiment shown in FIG. 1 is used as a solar cell module or a solar cell submodule constituting this solar cell module. For example, a substantially rectangular metal substrate 15 and a metal substrate that are grounded An insulating layer-equipped substrate 10 (hereinafter simply referred to as substrate 10) formed on the insulating layer 16, a stress relaxation layer 50 formed on the insulating layer 16, and a stress relaxation layer 50; Power generation comprising a plurality of power generation cells (solar battery cells) 54 connected in series, a first conductive member 42 connected to one of the plurality of power generation cells 54, and a second conductive member 44 connected to the other side Layer 56. In addition, although what consists of each part of the one electric power generation cell 54, the board | substrate 10 corresponding to this, and the stress relaxation layer 50 is called the photoelectric conversion element 40 here, the thin film solar cell 30 itself shown in FIG. You may call it a conversion element.

First, the board | substrate used for the thin film solar cell which has a photoelectric conversion element which concerns on embodiment of this invention is demonstrated.
Fig.2 (a) is typical sectional drawing which shows the board | substrate used for the thin film solar cell which has a photoelectric conversion element which concerns on embodiment of this invention shown in FIG. 1, (b) is embodiment of this invention. It is a typical sectional view showing other examples of a substrate used for a thin film solar cell which has such a photoelectric conversion element.

As shown in FIG. 2 (a), the substrate 10 includes a metal substrate 15 composed of a metal substrate 12 and an aluminum substrate 14 (hereinafter referred to as an Al substrate 14) mainly composed of aluminum, and an insulating layer 16. A substrate with an insulating layer.
In the substrate 10, an Al base 14 is formed on the surface 12 a of the metal base 12 to constitute a metal substrate 15, and an insulating layer 16 is formed on the surface 14 a of the Al base 14 of the metal substrate 15. Further, the metal substrate 15 is a laminate in which the metal base 12 and the Al base 14 are laminated and integrated, that is, an Al clad base or an Al clad substrate.

  The board | substrate 10 of this embodiment is utilized for the board | substrate of a photoelectric conversion element and a thin film solar cell, for example, is flat form. The shape, size, and the like of the substrate 10 are appropriately determined according to the size of the applied photoelectric conversion element and thin film solar cell. When used for a thin film solar cell, the substrate 10 has, for example, a rectangular shape or a rectangular shape in which the length of one side exceeds 1 m.

In the substrate 10, a flat or foil-like metal material is used for the metal base 12, and for example, a steel material such as carbon steel and ferritic stainless steel is used.
The steel material used for the metal base 12 has higher heat resistance at 300 ° C. or higher than the aluminum alloy, and the substrate 10 can obtain predetermined heat resistance.

As the carbon steel used for the metal base 12 described above, for example, carbon steel for mechanical structure having a carbon content of 0.6% by mass or less is used. As carbon steel for machine structure, what is generally called SC material is used, for example.
Moreover, as a ferritic stainless steel, SUS430, SUS405, SUS410, SUS436, SUS444, etc. can be used.
In addition to this, what is generally called SPCC (cold rolled steel sheet) is used as the steel material.

In addition to the above, the metal substrate 12 may be made of Kovar alloy (5 × 10 ⁻⁶ / ° C.), titanium, or a titanium alloy. As titanium, pure Ti (9.2 × 10 ⁻⁶ / ° C.) is used, and as a titanium alloy, Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn, which are wrought alloys, are used. . These metals are also used in a flat plate shape or a foil shape.
The metal substrate 12 is preferably a metal or alloy having a smaller coefficient of thermal expansion, higher rigidity, and higher heat resistance than aluminum and aluminum alloys.

Since the thickness of the metal substrate 12 affects the flexibility, it is preferable to make it thin within a range that does not involve an excessive lack of rigidity.
In the board | substrate 10 of this embodiment, the thickness of the metal base material 12 is 10-800 micrometers, for example, Preferably it is 30-300 micrometers. More preferably, it is 50-150 micrometers. It is preferable to reduce the thickness of the metal substrate 12 from the viewpoint of raw material costs.
When the metal substrate 12 is flexible, that is, flexible, the metal substrate 12 is preferably ferritic stainless steel.

The Al base material 14 is composed of aluminum (Al) as a main component, and aluminum as a main component means that the aluminum content is 90% by mass or more.
As the Al base material 14, for example, aluminum or an aluminum alloy is used. The aluminum or aluminum alloy used for the Al substrate 14 preferably does not contain unnecessary intermetallic compounds. Specifically, aluminum having a purity of 99% by mass or more with few impurities is preferable. As purity, for example, 99.99 mass% Al, 99.96 mass% Al, 99.9 mass% Al, 99.85 mass% Al, 99.7 mass% Al, 99.5 mass% Al, etc. are preferable. . Moreover, what added the element which is hard to make an intermetallic compound can be used for an aluminum alloy. For example, it is an aluminum alloy obtained by adding 2.0 to 7.0% by mass of magnesium to Al having a purity of 99.9% by mass. In addition to magnesium, elements having a high solid solubility limit such as Cu and Si can be added.

  By increasing the purity of the aluminum of the Al base 14, it is possible to avoid intermetallic compounds resulting from precipitates, and to increase the soundness of the insulating layer 16. This is because, when anodizing of an aluminum alloy is performed, an intermetallic compound may be the starting point, which may cause insulation failure. If there are many intermetallic compounds, the possibility increases.

Moreover, the thickness of Al base material 14 is 5-150 micrometers, for example, Preferably it is 10-100 micrometers. More preferably, it is 20-50 micrometers.
Moreover, the surface roughness of the Al base 14 is, for example, 1 μm or less in terms of arithmetic average roughness Ra. Preferably, it is 0.5 μm or less, more preferably 0.1 μm or less.
Note that the surface of the Al base 14 may be mirror-finished. This mirror finish is performed, for example, by the methods described in Japanese Patent No. 4212621, Japanese Patent Application Laid-Open No. 2003-341696, Japanese Patent Application Laid-Open No. 7-331379, Japanese Patent Application Laid-Open No. 2007-196250, and Japanese Patent Application Laid-Open No. 2000-223205. The

In the substrate 10, the insulating layer 16 is for preventing insulation and damage due to mechanical shock during handling. This insulating layer 16 is composed of an anodized film (aluminum anodized film (alumina film)).
The insulating layer 16 is not limited to the anodic oxide film, and may be formed by, for example, vapor deposition, sputtering, or CVD.

The thickness of the insulating layer 16 is preferably 5 μm or more, and more preferably 10 μm or more. When the thickness of the insulating layer 16 is excessively large, it is not preferable because flexibility is lowered and cost and time required for forming the insulating layer 16 are required. In practice, the thickness of the insulating layer 16 is 50 μm or less, preferably 30 μm or less at maximum. For this reason, the preferable thickness of the insulating layer 16 is 0.5-50 micrometers.
Further, the surface roughness of the surface 18a of the insulating layer 16 is, for example, an arithmetic average roughness Ra of 1 μm or less, preferably 0.5 μm or less, more preferably 0.1 μm or less.

The substrate 10 needs to have a tensile strength of 5 MPa or more, preferably 10 MPa or more, while being heat-treated at 500 ° C. or more.
Further, in order to prevent creep deformation during heat treatment at 500 ° C. or higher, it is preferable that the strength causing plastic deformation of 0.1% at the maximum when held at 500 ° C. for 10 minutes is 0.2 MPa or higher. More preferably, it is 0.4 MPa or more, and further preferably 1 MPa or more.

In addition, the board | substrate 10 becomes flexible as the board | substrate 10 whole by making all the metal base material 12, the Al base material 14, and the insulating layer 16 have flexibility, ie, a flexible thing. Thereby, for example, a stress relaxation layer, a back electrode serving as a lower electrode, a photoelectric conversion layer, a transparent electrode serving as an upper electrode, and the like are formed on the insulating layer 16 side of the substrate 10 by a roll-to-roll method. Can do.
Further, in the present embodiment, the substrate 10 is formed on the metal substrate 15 in which the metal base 12 and the Al base 14 are laminated and integrated, and the surface 14a of the Al base 14 of the metal substrate 15. By using an insulating layer-equipped substrate including the insulating layer 16, for example, high insulating properties and high strength can be maintained even after a film forming process at a temperature of 500 ° C. or higher, and the occurrence of strain is suppressed. It is possible to form various films at a high temperature of 500 ° C. or higher, for example, by a roll-to-roll method.

Further, the substrate 10 of the present embodiment is configured to include the metal substrate 15 having a two-layer structure of the metal substrate 12 and the Al substrate 14, but the present invention is not limited to the metal substrate 12 having at least one layer. Therefore, it is not limited to one layer, and a plurality of layers may be used.
Like the board | substrate 10a shown in FIG.2 (b), the metal base material may be 2 layer structure which has the 1st metal base material 13a and the 2nd metal base material 13b, for example.
In this case, for example, the first metal base 13 a is made of titanium or a titanium alloy, and the second metal base 13 b is made of a steel material like the metal base 12. The second metal base 13b may be made of titanium or a titanium alloy, and the first metal base 13a may be made of steel similarly to the metal base 12.
Furthermore, it is good also as a structure by which the Al base material 14 is formed in the surface 12a and back surface of the metal base material 12, and the insulating layer 16 is formed in the surface 14a of each Al base material 14 as a board | substrate. In this case, the Al base material 14 and the insulating layer 16 are formed symmetrically around the metal base material 12. In addition, what laminated | stacked and integrated the metal base material 12 and the two Al base materials 14 becomes a metal substrate.

Next, the manufacturing method of the board | substrate 10 of this embodiment is demonstrated.
First, the metal substrate 12 is prepared. The metal base 12 is formed in a predetermined shape and size depending on the size of the substrate 10 to be formed.
Next, the Al base material 14 is formed on the surface 12 a of the metal base material 12. Thereby, the metal substrate 15 is configured.
The method for forming the Al base material 14 on the surface 12a of the metal base material 12 is particularly limited as long as an integrated bond capable of ensuring the adhesion between the metal base material 12 and the Al base material 14 is achieved. is not. As a method for forming the Al base material 14, for example, a vapor phase method such as an evaporation method or a sputtering method, a plating method, and a pressure bonding method after surface cleaning can be used. As a method for forming the Al base material 14, pressure bonding by roll rolling or the like is preferable from the viewpoint of cost and mass productivity.
As described above, the Al base material 14 may be formed on both the front surface 12a and the back surface of the metal base material 12.

  Next, the insulating layer 16 is formed on the surface 14 a of the Al base 14 of the metal substrate 15. In this way, the substrate 10 is obtained. Hereinafter, a method of forming the anodic oxide film that is the insulating layer 16 will be described.

When forming the anodic oxide film which is the insulating layer 16, the anodic oxide film can be formed by using the metal substrate 12 as an anode, immersing it in an electrolyte together with a cathode, and applying a voltage between the anode and the cathode. At this time, when the metal substrate 12 comes into contact with the electrolyte, in order to form a local battery with the Al substrate 14, the metal substrate 12 in contact with the electrolyte is masked and insulated by a masking film (not shown). It is necessary to keep. That is, it is necessary to insulate the end surface and the back surface of the metal substrate 12 other than the surface 14a of the Al substrate 14 using a masking film (not shown).
Prior to the anodizing treatment, the surface of the Al base 14 is subjected to cleaning treatment, polishing smoothing treatment, or the like as necessary.

Carbon, Al, or the like is used as a cathode during anodization. As the electrolyte, an acidic electrolytic solution containing one or more acids such as sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, and amidesulfonic acid is used. Anodizing conditions are not particularly limited by the type of electrolyte used. As anodizing conditions, for example, electrolyte concentration 1 to 80% by mass, liquid temperature 5 to 70 ° C., current density 0.005 to 0.60 A / cm ² , voltage 1 to 200 V, electrolysis time 3 to 500 minutes It is appropriate if it exists. As the electrolyte, sulfuric acid, phosphoric acid, oxalic acid or a mixture thereof is preferable. When such an electrolyte is used, the electrolyte concentration is preferably 4 to 30% by mass, the liquid temperature is 10 to 30 ° C., the current density is 0.002 to 0.30 A / cm ² , and the voltage is 20 to 100V.

During the anodizing treatment, an oxidation reaction proceeds in a substantially vertical direction from the surface 14a of the Al base material 14, and an anodized film is generated on the surface 14a of the Al base material 14. When the above acidic electrolytic solution is used, the anodic oxide film has a fine columnar body having a substantially regular hexagonal shape in plan view arranged without gaps, and has a round bottom at the center of each fine columnar body. Holes are formed, and a porous type in which a barrier layer (usually 0.02 to 0.1 μm in thickness) is formed at the bottom of the fine columnar body.
Such an anodic oxide film having a porous structure has a low Young's modulus of the film compared to a non-porous aluminum oxide single film, and has a high resistance to bending and cracking caused by a difference in thermal expansion at high temperatures. Become.

When electrolytic treatment is carried out with a neutral electrolytic solution such as boric acid without using an acidic electrolytic solution, a dense anodic oxide film (non-porous aluminum oxide simple substance film) is formed instead of an anodic oxide film in which porous fine columnar bodies are arranged. Become. After the porous anodic oxide film is formed with the acidic electrolytic solution, an anodic oxide film having a thicker barrier layer may be formed by a pore filling method in which re-electrolytic treatment is performed with the neutral electrolytic solution. By increasing the thickness of the barrier layer, it is possible to obtain a coating with higher insulation.
As the electrolytic solution used for the anodizing treatment, an aqueous sulfuric acid solution or an aqueous oxalic acid solution is preferably used. An oxalic acid aqueous solution is excellent in soundness of the anodic oxide film, and a sulfuric acid aqueous solution is excellent in continuous treatment productivity.
The preferable thickness of the anodic oxide film that is the insulating layer 16 is 0.5 to 50 μm as described above. This thickness is controllable by constant current electrolysis, constant voltage electrolysis current, voltage magnitude, and electrolysis time.

The insulating layer 16 formed by anodic oxidation is subjected to sealing treatment in a boric acid solution when it is particularly desired to enhance the insulation.
As the sealing treatment, an electrochemical method or a chemical method is known, and an electrochemical method (anodic treatment) using aluminum or an aluminum alloy as an anode is particularly preferable.
The electrochemical method is preferably a method in which aluminum or an alloy thereof is used as an anode and a direct current is applied to perform sealing treatment. The electrolytic solution is preferably an aqueous boric acid solution, and is preferably an aqueous solution obtained by adding a borate containing sodium to an aqueous boric acid solution. Examples of borates include disodium octaborate, sodium tetraphenylborate, sodium tetrafluoroborate, sodium peroxoborate, sodium tetraborate, and sodium metaborate. These borates are available as anhydrous or hydrated.

As an electrolytic solution used for the sealing treatment, it is particularly preferable to use an aqueous solution obtained by adding 0.01 to 0.5 mol / L sodium tetraborate to a 0.1 to 2 mol / L boric acid aqueous solution. It is preferable that 0 to 0.1 mol / L of aluminum ion is dissolved. Aluminum ions are chemically or electrochemically dissolved in the electrolytic solution by a sealing treatment, and a method of electrolyzing by adding aluminum borate in advance is particularly preferable. Further, trace elements contained in the aluminum alloy may be dissolved.
Preferred sealing treatment conditions are a liquid temperature of 10 to 55 ° C. (particularly preferably 10 to 30 ° C.), a current density of 0.01 to 5 A / dm ² (particularly preferably 0.1 to 3 A / dm ² ), and an electrolytic treatment time. 0.1 to 10 minutes (particularly preferably 1 to 5 minutes).

As the current, an alternating current, a direct current, or an AC / DC superimposed current can be used. The method of applying the current may be constant or gradually increasing from the initial stage of electrolysis, but a method using direct current is particularly preferable. Either a constant voltage method or a constant current method may be used for applying the current.
At this time, the voltage between the substrate and the counter electrode is preferably 100 to 1000 V, and the voltage depends on the electrolytic bath composition, the liquid temperature, the flow velocity at the aluminum interface, the power waveform, the distance between the substrate and the counter electrode, the electrolysis time, and the like. Change.
As the electrolyte flow rate on the substrate surface and the method of giving the flow rate, the electrolytic bath, the electrode, and the concentration control method of the electrolytic solution can use the known anodizing method and the sealing method described in the anodizing treatment. It is. The film thickness when anodizing in a boric acid aqueous solution containing sodium borate is preferably 100 nm or more, and more preferably 300 nm or more. The upper limit is the film thickness of the porous anodic oxide film. Thereby, it can use for the board | substrate of a thin film solar cell which requires especially high temperature intensity | strength and has the merit of flexibility.

In addition, a chemically preferable method may be a structure in which pores and / or vacancies are filled with Si oxide after anodizing. For filling with Si oxide, a solution containing a compound having a Si—O bond is applied, or a sodium silicate aqueous solution (No. 1 sodium silicate or No. 3 sodium silicate, 1 to 5 mass% aqueous solution, 20 to 70 ° C.) is 1 A method of washing and drying after immersing for ˜30 seconds and further baking at 200 to 600 ° C. for 1 to 60 minutes is also possible.
As a chemically preferable method, in addition to the sodium silicate aqueous solution, the concentration of sodium fluoride zirconate and / or sodium dihydrogen phosphate alone or a mixed aqueous solution having a mixing ratio of 5: 1 to 1: 5 by weight A method of performing a sealing treatment by immersing in 1 to 5% by mass of a liquid at 20 to 70 ° C. for 1 to 60 seconds can also be used.
In addition, about an anodizing process, it can carry out with the well-known what is called a roll-to-roll system anodizing apparatus, for example.

  Next, after the anodizing treatment, the masking film (not shown) is peeled off. Thereby, the substrate 10 can be formed.

Next, the photoelectric conversion element 40 of the thin film solar cell 30 of this embodiment shown in FIG. 1 will be described.
In the thin film solar cell (for example, the thin film solar cell submodule) 30 of this embodiment, the stress relaxation layer 50 is formed on the surface of the substrate 10 described above, that is, the surface 16a of the insulating layer 16.
The thin film solar cell 30 includes a plurality of photoelectric conversion elements 40, a first conductive member 42, and a second conductive member 44.

The photoelectric conversion element 40 constitutes the thin-film solar cell 30, and includes a power generation cell (substrate 10, a stress relaxation layer 50, a back electrode 32, a photoelectric conversion layer 34, a buffer layer 36, and a transparent electrode 38). Solar cell) 54.
As described above, the stress relaxation layer 50 is formed on the surface 16 a of the insulating layer 16. On the surface 50 a of the stress relaxation layer 50, the back electrode 32, the photoelectric conversion layer 34, the buffer layer 36, and the transparent electrode 38 of the power generation cell 54 are sequentially stacked.

  The back electrode 32 is formed on the surface 50 a of the stress relaxation layer 50 by providing an adjacent back electrode 32 and a separation groove (P 1) 33. A photoelectric conversion layer 34 is formed on the back electrode 32 while filling the separation groove (P1) 33. A buffer layer 36 is formed on the surface of the photoelectric conversion layer 34. The photoelectric conversion layer 34 and the buffer layer 36 are separated from other photoelectric conversion layers 34 and the buffer layer 36 by a groove (P2) 37 reaching the back electrode 32. The groove (P2) 37 is formed at a position different from the separation groove (P1) 33 of the back electrode 32.

A transparent electrode 38 is formed on the surface of the buffer layer 36 while filling the groove (P2) 37.
An opening groove (P3) 39 that penetrates the transparent electrode 38, the buffer layer 36, and the photoelectric conversion layer 34 and reaches the back electrode 32 is formed. In the thin film solar cell module 30, each photoelectric conversion element 40 is electrically connected in series in the longitudinal direction L of the substrate 10 by the back electrode 32 and the transparent electrode 38.

The photoelectric conversion element 40 of this embodiment is called an integrated photoelectric conversion element (solar cell). For example, the back electrode 32 is composed of a molybdenum electrode, and the photoelectric conversion layer 34 is a semiconductor having a photoelectric conversion function. A compound, for example, is composed of a CIGS layer, the buffer layer 36 is composed of CdS, and the transparent electrode 38 is composed of ZnO.
The photoelectric conversion element 40 is formed to extend in the width direction perpendicular to the longitudinal direction L of the substrate 10. For this reason, the back electrode 32 and the like also extend long in the width direction of the substrate 10.

  As shown in FIG. 1, a first conductive member 42 is connected on the back electrode 32 at the right end. The first conductive member 42 is for taking out an output from a negative electrode to be described later. Originally, the photoelectric conversion element 40 is formed on the back electrode 32 at the right end. For example, the photoelectric conversion element 40 is removed by laser scribing or mechanical scrubbing to expose the back electrode 32.

  The first conductive member 42 is, for example, an elongated belt-like member, extends in a substantially linear shape in the width direction of the substrate 10, and is connected to the right end back electrode 32. As shown in FIG. 1, the first conductive member 42 is, for example, a copper ribbon 42a covered with an indium copper alloy coating 42b. The first conductive member 42 is connected to the back electrode 32 by, for example, ultrasonic soldering.

  The second conductive member 44 is for taking out an output from a positive electrode described later to the outside. Similarly to the first conductive member 42, the second conductive member 44 is an elongated belt-like member, extends substantially linearly in the width direction of the substrate 10, and is connected to the back electrode 32 at the left end. Originally, the photoelectric conversion element 40 is formed on the leftmost back electrode 32. For example, the photoelectric conversion element 40 is removed by laser scribing or mechanical scrub, and the back electrode 32 is exposed.

The second conductive member 44 has the same configuration as the first conductive member 42. For example, a copper ribbon 44a is covered with a coating material 44b of indium copper alloy.
The first conductive member 42 and the second conductive member 44 may be tin-plated copper ribbons. Further, the connection between the first conductive member 42 and the second conductive member 44 is not limited to the ultrasonic soldering. For example, the first conductive member 42 and the second conductive member 44 may be connected using a conductive adhesive or a conductive tape.

In addition, the photoelectric conversion layer 34 of the photoelectric conversion element 40 of this embodiment is comprised by CIGS, for example, and can be manufactured with the manufacturing method of a well-known CIGS type solar cell.
The separation groove (P1) 33 of the back electrode 32, the groove (P2) 37 reaching the back electrode 32, and the opening groove (P3) 39 reaching the back electrode 32 can be formed by laser scribe or mechanical scribe.

  In the thin film solar cell 30, when light is incident on the photoelectric conversion element 40 from the transparent electrode 38 side, this light passes through the transparent electrode 38 and the buffer layer 36, and an electromotive force is generated in the photoelectric conversion layer 34. A current from the transparent electrode 38 toward the back electrode 32 is generated. The arrows shown in FIG. 1 indicate the direction of current, and the direction of movement of electrons is opposite to the direction of current. For this reason, in the photoelectric conversion unit 48, the leftmost back electrode 32 in FIG. 1 becomes a positive electrode (plus electrode), and the rightmost back electrode 32 becomes a negative electrode (minus electrode).

In the present embodiment, the electric power generated in the thin film solar cell 30 can be taken out of the thin film solar cell 30 from the first conductive member 42 and the second conductive member 44.
In the present embodiment, the first conductive member 42 is a negative electrode, and the second conductive member 44 is a positive electrode. Further, the first conductive member 42 and the second conductive member 44 may have opposite polarities, and are appropriately changed according to the configuration of the photoelectric conversion element 40, the configuration of the thin film solar cell 30, and the like.
Further, in the present embodiment, each photoelectric conversion element 40 is formed to be connected in series in the longitudinal direction L of the substrate 10 by the back electrode 32 and the transparent electrode 38, but is not limited thereto. For example, each photoelectric conversion element 40 may be formed such that each photoelectric conversion element 40 is connected in series in the width direction by the back electrode 32 and the transparent electrode 38.

  In the photoelectric conversion element 40, the back electrode 32 and the transparent electrode 38 are for taking out current generated in the photoelectric conversion layer 34. Both the back electrode 32 and the transparent electrode 38 are made of a conductive material. The transparent electrode 38 on the light incident side needs to have translucency.

The back electrode 32 is made of, for example, Mo, Cr, or W and a combination thereof. The back electrode 32 may have a single layer structure or a laminated structure such as a two-layer structure. The back electrode 32 is preferably composed of Mo.
The back electrode 32 preferably has a thickness of 100 nm or more, and more preferably 0.45 to 1.0 μm.
Moreover, the formation method of the back surface electrode 32 is not specifically limited, It can form by vapor phase film-forming methods, such as an electron beam vapor deposition method and sputtering method.

The transparent electrode 38 is made of, for example, ZnO to which Al, B, Ga, Sb or the like is added, ITO (indium tin oxide), SnO ₂ or a combination thereof. The transparent electrode 38 may have a single layer structure or a laminated structure such as a two-layer structure. Further, the thickness of the transparent electrode 38 is not particularly limited, and is preferably 0.3 to 1 μm.
The method for forming the transparent electrode 38 is not particularly limited, and can be formed by a vapor deposition method such as an electron beam evaporation method or a sputtering method, or a coating method.

The buffer layer 36 is formed to protect the photoelectric conversion layer 34 when the transparent electrode 38 is formed and to transmit light incident on the transparent electrode 38 to the photoelectric conversion layer 34.
The buffer layer 36 is made of, for example, CdS, ZnS, ZnO, ZnMgO, ZnS (O, OH), or a combination thereof.
The buffer layer 36 preferably has a thickness of 30 to 100 nm. The buffer layer 36 is formed by, for example, a CBD (chemical bath) method.

  The photoelectric conversion layer 34 is a layer that generates a current by absorbing light that has passed through the transparent electrode 38 and the buffer layer 36, and has a photoelectric conversion function. In the present embodiment, the configuration of the photoelectric conversion layer 34 is not particularly limited, and includes, for example, at least one compound semiconductor having a chalcopyrite structure. Further, the photoelectric conversion layer 34 may be at least one compound semiconductor composed of a group Ib element, a group IIIb element, and a group VIb element.

Further, since the light absorption rate is high and high photoelectric conversion efficiency is obtained, the photoelectric conversion layer 34 is composed of at least one group Ib element selected from the group consisting of Cu and Ag, and a group consisting of Al, Ga, and In. It is preferably at least one compound semiconductor composed of at least one type IIIb group element selected more and at least one type VIb group element selected from the group consisting of S, Se and Te. As this compound semiconductor, CuAlS ₂ , CuGaS ₂ , CuInS ₂ , CuAlSe ₂ , CuGaSe ₂ , CuInSe ₂ (CIS), AgAlS ₂ , AgGaS ₂ , AgInS ₂ , AgAlSe ₂ , AgGaSe ₂ , AgInSe ₂ , AgInSe ₂ , AgInSe ₂ , AgInSe ₂ , AgInT , AgInTe ₂ , Cu (In _1-x Ga _x ) Se ₂ (CIGS), Cu (In _1-x Al _x ) Se ₂ , Cu (In _1-x Ga _x ) (S, Se) ₂ , Ag (In _1-x Ga _x ) Se ₂ , Ag (In _1-x Ga _x ) (S, Se) _{2 and the} like.

The photoelectric conversion layer 34 particularly preferably includes CuInSe ₂ (CIS) and / or Cu (In, Ga) Se ₂ (CIGS) in which Ga is dissolved. CIS and CIGS are semiconductors having a chalcopyrite crystal structure, have high light absorption, and high photoelectric conversion efficiency has been reported. Moreover, there is little degradation of efficiency by light irradiation etc. and it is excellent in durability.

The photoelectric conversion layer 34 contains impurities for obtaining a desired semiconductor conductivity type. Impurities can be contained in the photoelectric conversion layer 34 by diffusion from adjacent layers and / or active doping. In the photoelectric conversion layer 34, the constituent elements and / or impurities of the I-III-VI group semiconductor may have a concentration distribution, and a plurality of layer regions having different semiconductor properties such as n-type, p-type, and i-type May be included.
For example, in the CIGS system, when the Ga amount in the photoelectric conversion layer 34 has a distribution in the thickness direction, the band gap width / carrier mobility and the like can be controlled, and the photoelectric conversion efficiency can be designed high.

The photoelectric conversion layer 34 may include one or more semiconductors other than the I-III-VI group semiconductor. As a semiconductor other than the I-III-VI group semiconductor, a semiconductor composed of a group IVb element such as Si (group IV semiconductor), a semiconductor composed of a group IIIb element such as GaAs and a group Vb element (group III-V semiconductor), and Examples thereof include semiconductors (II-VI group semiconductors) composed of IIb group elements such as CdTe and VIb group elements. The photoelectric conversion layer 34 may contain an optional component other than a semiconductor and impurities for obtaining a desired conductivity type as long as the characteristics are not hindered.
Further, the content of the I-III-VI group semiconductor in the photoelectric conversion layer 34 is not particularly limited. 75 mass% or more is preferable, as for content of the I-III-VI group semiconductor in the photoelectric converting layer 34, 95 mass% or more is more preferable, and 99 mass% or more is especially preferable.

  In the present embodiment, when the photoelectric conversion layer 34 is composed of a compound semiconductor whose main component (75% by mass or more) is CdTe, the metal substrate 12 is composed of carbon steel or ferritic stainless steel. Is preferred.

  As CIGS layer deposition methods, 1) multi-source co-evaporation, 2) selenization, 3) sputtering, 4) hybrid sputtering, and 5) mechanochemical process are known.

1) As a multi-source simultaneous vapor deposition method,
Three-stage method (JRTuttle et.al, Mat.Res.Soc.Symp.Proc., Vol.426 (1996) p.143. Etc.) and EC group co-evaporation method (L. Stolt et al .: Proc. 13th ECPVSEC (1995, Nice) 1451, etc.).
In the former three-stage method, In, Ga, and Se are first co-deposited at a substrate temperature of 300 ° C. in a high vacuum, and then heated to 500 to 560 ° C., and Cu and Se are co-evaporated. In this method, Ga and Se are further vapor-deposited. The latter EC group simultaneous vapor deposition method is a method in which Cu-excess CIGS is vapor-deposited in the early stage of vapor deposition and In-rich CIGS is vapor-deposited in the latter half.

In order to improve the crystallinity of the CIGS film, as a method of improving the above method,
a) a method using ionized Ga (H. Miyazaki, et.al, phys.stat.sol. (a), Vol.203 (2006) p.2603, etc.),
b) Method of using cracked Se (68th Japan Society of Applied Physics Academic Lecture Proceedings (Autumn 2007, Hokkaido Institute of Technology) 7P-L-6 etc.),
c) Method using radicalized Se (Proceedings of the 54th Japan Society of Applied Physics (Aoyama Gakuin University) 29P-ZW-10 etc.)
d) A method using a photoexcitation process (the 54th Japan Society of Applied Physics Academic Lecture Proceedings (Spring 2007 Aoyama Gakuin University) 29P-ZW-14 etc.) is known.

2) The selenization method is also called a two-step method. First, a metal precursor of a laminated film such as a Cu layer / In layer or a (Cu—Ga) layer / In layer is formed by sputtering, vapor deposition, or electrodeposition. This is a method of forming a selenium compound such as Cu (In _1-x Ga _x ) Se ₂ by a thermal diffusion reaction by forming a film and heating it in selenium vapor or hydrogen selenide to about 450 to 550 ° C. . This method is called a vapor phase selenization method. In addition, there is a solid-phase selenization method in which solid-phase selenium is deposited on a metal precursor film and selenized by a solid-phase diffusion reaction using the solid-phase selenium as a selenium source.

  In the selenization method, in order to avoid the rapid volume expansion that occurs during selenization, a method of previously mixing selenium in a metal precursor film at a certain ratio (T. Nakada et.al, Solar Energy Materials and Solar Cells 35 (1994) 204-214, etc.), and multilayer precursor film with selenium sandwiched between thin metal layers (for example, Cu layer / In layer / Se layer ... stacked with Cu layer / In layer / Se layer) (T. Nakada et.al, Proc. Of 10th European Photovoltaic Solar Energy Conference (1991) 887-890. Etc.) is known.

  In addition, as a method for forming a graded band gap CIGS film, a Cu—Ga alloy film is first deposited, an In film is deposited thereon, and when this is selenized, natural thermal diffusion is used to form Ga. There is a method in which the concentration is inclined in the film thickness direction (K. Kushiya et.al, Tech.Digest 9th Photovoltaic Science and Engineering Conf. Miyazaki, 1996 (Intn. PVSEC-9, Tokyo, 1996) p.149.).

3) As a sputtering method,
A method using CuInSe ₂ polycrystal as a target, a two-source sputtering method using Cu ₂ Se and In ₂ Se ₃ as a target and a H ₂ Se / Ar mixed gas as a sputtering gas (JHErmer, et.al, Proc. 18th IEEE Photovoltaic Specialists Conf. (1985) 1655-1658. Etc.), and a three-source sputtering method in which a Cu target, an In target, and a Se or CuSe target are sputtered in Ar gas (T. Nakada, et.al, Jpn. J. Appl. Phys. 32 (1993) L1169-L1172.

  4) As the hybrid sputtering method, in the sputtering method described above, Cu and In metal are DC sputtering, and only Se is vapor deposition (T. Nakada, et.al., Jpn.Appl.Phys.34 ( 1995) 4715-4721.

  5) In the mechanochemical process method, raw materials corresponding to the CIGS composition are put into a planetary ball mill container, and the raw materials are mixed by mechanical energy to obtain CIGS powder, which is then applied onto the substrate by screen printing and annealed. To obtain a CIGS film (T. Wada et.al, Phys.stat.sol. (A), Vol.203 (2006) p2593, etc.).

  Examples of other CIGS film formation methods include screen printing, proximity sublimation, MOCVD, and spray (wet film formation). For example, a fine particle film containing a group Ib element, a group IIIb element, and a group VIb element is formed on a substrate by a screen printing method (wet film forming method) or a spray method (wet film forming method), and then pyrolyzed ( At this time, a crystal having a desired composition can be obtained by performing a thermal decomposition treatment in a VIb group element atmosphere (JP-A-9-74065, JP-A-9-74213, etc.).

Moreover, in this embodiment, it is preferable that the difference of the thermal expansion coefficient of the metal base material 12 and the photoelectric converting layer 34 is less than 3 * 10 < ^-6 > / ^degreeC .
The thermal expansion coefficient of the main compound semiconductor used as the photoelectric conversion layer 34 is 5.8 × 10 ⁻⁶ / ° C. for GaAs, which is representative of the III-V group, and 4. for CdTe, which is representative of the II-VI group. It is 5 × 10 ⁻⁶ / ° C. and 10 × 10 ⁻⁶ / ° C. for Cu (InGa) Se ₂ which is a representative of the I-III-VI group.
When the compound semiconductor is formed as a photoelectric conversion layer 34 on the substrate 10 at a high temperature of 500 ° C. or higher and then cooled to room temperature, if the difference in thermal expansion from the metal substrate 12 is large, film formation defects such as peeling may occur. Arise. Moreover, the photoelectric conversion efficiency of the photoelectric converting layer 34 may fall by the strong internal stress in the compound semiconductor resulting from a thermal expansion difference with the metal base material 12. When the difference in thermal expansion coefficient between the metal substrate 12 and the photoelectric conversion layer 34 (compound semiconductor) is less than 3 × 10 ⁻⁶ / ° C., film formation defects such as peeling are unlikely to occur, which is preferable. More preferably, the difference in thermal expansion coefficient is less than 1 × 10 ⁻⁶ / ° C. Here, the thermal expansion coefficient and the difference between the thermal expansion coefficients are both room temperature (23 ° C.) values.

The stress relaxation layer 50 prevents peeling of each layer constituting the photoelectric conversion element 40.
When the layers constituting the photoelectric conversion element 40 are formed by the stress relaxation layer 50, for example, when the temperature is lowered to room temperature after being heated to a temperature of 500 ° C. or higher, the stress generated in the insulating layer 16 is relaxed. Thus, generation of cracks in the insulating layer 16 and generation of peeling at the interface between the insulating layer 16 and the Al base 12 can be suppressed.

The stress relaxation layer 50 preferably has a thermal expansion coefficient smaller than that of the photoelectric conversion layer 34 and larger than that of the insulating layer 16. Moreover, it is preferable that the difference between the thermal expansion coefficient of the photoelectric conversion layer 34 of the photoelectric conversion element 40 and the thermal expansion coefficient of the metal substrate 15 is small as described above.
Therefore, the stress relaxation layer 50 has a thermal expansion coefficient intermediate between the thermal expansion coefficient of the insulating layer 16 of the substrate 10, the thermal expansion coefficient of the photoelectric conversion layer 34 of the photoelectric conversion element 40, and the thermal expansion coefficient of the metal substrate 15. It is preferable that

The metal substrate 15 is configured to include the metal base 12 and the Al base 14, but the thermal expansion coefficient of the metal substrate 15 is preferably obtained by two-layer stress calculation. Alternatively, the metal substrate 15 may be prepared in advance and the thermal expansion coefficient may be measured.
When the metal substrate 12 is a steel material and the thickness thereof is sufficiently thicker than that of the Al substrate 14, for example, when the metal substrate 12 is five times thicker than the Al substrate 14, the metal substrate 12 The thermal expansion coefficient of the material 12 can be used as the thermal expansion coefficient of the metal substrate 15.

  If the thermal expansion coefficient of the stress relaxation layer 50 is intermediate between the thermal expansion coefficient of the insulating layer 16 of the substrate 10, the thermal expansion coefficient of the photoelectric conversion layer 34 of the photoelectric conversion element 40, and the thermal expansion coefficient of the metal substrate 15. The composition is not particularly limited, and is appropriately selected according to the composition of the photoelectric conversion layer 34.

In addition, the inventor of the present application has heated the anodic oxide film formed on the Al base 14 of the alloy steel plate (metal base 12) selected so as to match the thermal expansion coefficient with the compound semiconductor layer to about 300 ° C. It has also been confirmed that no cracks occur. However, when the anodic oxide film is heated to 500 ° C. or higher, it is confirmed that cracks occur in the anodic oxide film and that peeling occurs between the anodic oxide film and the back electrode or between the compound semiconductor layers. Yes.
At a high temperature of 300 ° C. or higher, a crack occurs in the insulating layer (anodized film) formed on the Al base 14 of the substrate 10, and there is a gap between the back electrode and the photoelectric conversion layer (compound semiconductor film) formed thereon. The reason why peeling occurs is that the thermal expansion coefficient of the anodized film is 5 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the clad material of the alloy steel plate (metal base 12) and the Al base (10 × 10 ^{− 6} / ° C.), and it is considered that there is a difference with respect to the thermal expansion coefficient (10 × 10 ⁻⁶ / ° C.) of the CIGS layer which is a photoelectric conversion layer.
Moreover, the generation of cracks due to the difference in thermal expansion coefficient and the occurrence of peeling are particularly likely to occur in the oxide layer. Similarly, the back electrode having a small coefficient of thermal expansion is ductile because it is made of metal, and it is considered that peeling does not occur because it has higher resistance to stress than an oxide film.

  By providing the stress relaxation layer 50, even when stress is generated in the insulating layer 16 in the manufacturing process of each layer constituting the photoelectric conversion element 40 and when the temperature is lowered to room temperature, the generated stress is reduced. The generation of cracks in the insulating layer 16 and the occurrence of peeling between the insulating layer 16 and the back electrode are suppressed by being relaxed by the layer 50.

The stress relaxation layer 50 is preferably made of an oxide from the viewpoint of improving the insulating characteristics of the substrate 10 and the adhesion to the insulating layer 16.
As oxides, TiO ₂ (9.0 × 10 −6 / ° C.), ZrO ₂ (7.6 × 10 ⁻⁶ / ° C.), HfO ₂ (6.5 × 10 ⁻⁶ / ° C.), Al ₂ O ₃ (8.4 × 10 ⁻⁶ / ° C.) can be used.

The stress relaxation layer 50 may be made of nitride. In this case, the ^{nitride, TiN (9.4 × 10 -6 /℃),ZrN(7.2×10} -6 /℃),BN(6.4×10 -6 / ℃), AlN (5 7 × 10 ⁻⁶ / ° C.). Even if nitride is used, the insulating properties of the substrate 10 can be improved.
The stress relaxation layer 50 has a thermal expansion coefficient between the thermal expansion coefficient of the insulating layer 16 of the substrate 10, the thermal expansion coefficient of the photoelectric conversion layer 34 of the photoelectric conversion element 40, and the thermal expansion coefficient of the metal substrate 15. Of course, it may be made of metal or alloy.

  Here, it is reported that the photoelectric conversion efficiency increases when alkali metal (Na) is diffused into the photoelectric conversion layer 34. For this reason, the stress relaxation layer 50 may function as a Na supply layer (alkali supply layer), and may diffuse the alkali metal (Na) into the photoelectric conversion layer 34 (CIGS layer). For this reason, it is preferable that the stress relaxation layer 50 contains an alkali metal. For example, the stress relaxation layer 50 is made of a compound containing silicon oxide as a main component and containing sodium oxide, for example, silicate glass such as blue plate glass (soda lime glass).

Specifically, as the stress relaxation layer 50, blue plate glass (soda lime glass) can be used.
Here, the thermal expansion coefficient of blue plate glass (soda lime glass) is 8 to 9.5 × 10 ⁻⁶ / ° C. The thermal expansion coefficient of the blue plate glass (soda lime glass) is intermediate between the thermal expansion coefficient of the insulating layer 16 of the substrate 10, the thermal expansion coefficient of the photoelectric conversion layer 34 of the photoelectric conversion element 40, and the thermal expansion coefficient of the metal substrate 15. Therefore, it is preferable.
Furthermore, when a blue plate glass (soda lime glass) is used as the stress relaxation layer 50, it is preferable because it has good insulating properties.

In the present embodiment, the stress relaxation layer 50 is not provided with a function of diffusing alkali metal into the photoelectric conversion layer 34. For example, a layer containing alkali metal is deposited on the back electrode 32 by vapor deposition or sputtering. You may form by a method. Further, after forming a precursor containing In, Cu and Ga metal elements as components on the back electrode 32, an aqueous solution containing, for example, sodium molybdate is attached to the precursor to form a layer. Also good.
Furthermore, as a configuration in which a layer containing one or more alkali metal compounds such as Na ₂ S, Na ₂ Se, NaCl, NaF, and sodium molybdate is provided inside the back electrode 32, an alkali metal is used. You may make it supply to the photoelectric converting layer 34. FIG.

The stress relaxation layer 50 is not limited to a single layer structure, and may have a two layer structure. In this case, if the layer on the substrate 10 side is the first stress relaxation layer and the layer above it is the second stress relaxation layer, the first stress relaxation layer has a thermal expansion higher than that of the second stress relaxation layer. Consists of small coefficients.
In this case, the relationship among the thermal expansion coefficients of the insulating layer 16, the first stress relaxation layer, the second stress relaxation layer, and the photoelectric conversion layer 34 is as follows.
Thermal expansion coefficient of insulating layer 16 <thermal expansion coefficient of first stress relaxation layer <thermal expansion coefficient of second stress relaxation layer <thermal expansion coefficient of photoelectric conversion layer 34

When the stress relaxation layer 50 has a two-layer structure, when the photoelectric conversion layer 34 is made of a CIGS semiconductor compound, the first stress relaxation layer on the substrate 10 side is ZrN, AlN, BN, Al _2. It is preferable that the second stress relaxation layer is composed of O ₃ or ZrO ₂ , and the second stress relaxation layer is a compound containing silicon oxide as a main component and containing sodium oxide, for example, silicic acid such as blue plate glass (soda lime glass). It is preferable to be comprised with salt glass.
Further, the thickness of the stress relaxation layer 50 is preferably 10 nm to 400 nm, more preferably 50 nm to 200 nm, whether it is a single layer or a multilayer.

Next, the manufacturing method of the thin film solar cell 30 of this embodiment is demonstrated.
First, the substrate 10 formed as described above is prepared.
Next, for example, a TiO ₂ film is formed as a stress relaxation layer 50 on the surface 16a of the insulating layer 16 of the substrate 10 by a sputtering method using a film forming apparatus.
Next, a molybdenum film to be the back electrode 32 is formed on the surface 50a of the stress relaxation layer 50 by, for example, a sputtering method using a film forming apparatus.
Next, the molybdenum film is scribed at a first position using, for example, a laser scribing method to form a separation groove (P1) 33 extending in the width direction of the substrate 10. Thereby, the back surface electrodes 32 separated from each other by the separation groove (P1) 33 are formed.

Next, for example, a CIGS layer that becomes the photoelectric conversion layer 34 (p-type semiconductor layer) is formed by any one of the above-described film formation methods so as to cover the back electrode 32 and fill the separation groove (P1) 33. It forms using a membrane apparatus.
Next, a CdS layer (n-type semiconductor layer) to be the buffer layer 36 is formed on the CIGS layer by, for example, a CBD (chemical bath) method. Thereby, a pn junction semiconductor layer is formed.
Next, a second position different from the first position of the separation groove (P1) 33 is scribed using a laser scribing method, and extends to the back surface electrode 32 extending in the width direction of the substrate 10 (P2). ) 37 is formed.

Next, a ZnO layer to which, for example, Al, B, Ga, Sb or the like to be the transparent electrode 38 is added so as to fill the groove (P2) 37 on the buffer layer 36 is formed using a film formation apparatus. It is formed by sputtering or coating.
Next, a third position different from the first position of the separation groove (P1) 33 and the second position of the groove (P2) 37 is scribed using a laser scribing method, and extends in the width direction of the substrate 10. Further, an opening groove (P3) 39 reaching the back electrode 32 is formed. Thus, the plurality of power generation cells 54 are formed on the laminate of the substrate 10 and the stress relaxation layer 50, and the power generation layer 56 is formed.

Next, the respective photoelectric conversion elements 40 formed on the left and right end electrodes 32 in the longitudinal direction L of the substrate 10 are removed by, for example, laser scribing or mechanical scrubbing to expose the back electrode 32. Next, the first conductive member 42 is connected to the back electrode 32 at the right end, and the second conductive member 44 is connected to the back electrode 32 at the left end using, for example, ultrasonic soldering.
Thereby, as shown in FIG. 1, the thin film solar cell 30 to which the some photoelectric conversion element 40 was electrically connected in series can be manufactured.

  Next, a sealing adhesive layer (not shown), a water vapor barrier layer (not shown) and a surface protective layer (not shown) are arranged on the surface side of the obtained thin film solar cell 30, and the back surface of the thin film solar cell 30. A sealing adhesive layer (not shown) and a back sheet (not shown) are arranged on the side, that is, the back side of the substrate 10, and are laminated by, for example, a vacuum laminating method. Thereby, a thin film solar cell module can be obtained.

  In the present embodiment, when the stress relaxation layer 50 is provided to form a back electrode, a CIGS layer (photoelectric conversion layer), a CdS buffer layer, a ZnO layer, a transparent electrode, etc. constituting the thin film solar cell, 500 ° C. or higher. Even after the temperature is raised to room temperature, even if the temperature is lowered to room temperature, the stress generated due to the difference in the thermal expansion coefficient of each layer can be relaxed, and peeling of each layer constituting the photoelectric conversion element 40 is suppressed. be able to. In particular, the stress generated in the insulating layer 16 can be relaxed, and the generation of cracks in the insulating layer 16 and the occurrence of peeling starting from the insulating layer 16 can be suppressed.

In the present embodiment, as described above, the substrate 10 is combined with the metal substrate 15 in which the metal base 12 and the Al base 14 are laminated and the surface 14a of the Al base 14 of the metal substrate 15. By using the substrate with an insulating layer provided with the insulating layer 16 formed in the above, for example, high insulation and high strength can be maintained even after a film forming process at a temperature of 500 ° C. or higher, and the temperature is 500 ° C. or higher. A manufacturing process at a high temperature is possible. For this reason, a compound semiconductor can be formed as a photoelectric conversion layer at 500 ° C. or higher. Since the compound semiconductor constituting the photoelectric conversion layer can be improved in photoelectric conversion characteristics when formed at a high temperature, the photoelectric conversion element 40 having the photoelectric conversion layer 34 with improved photoelectric conversion characteristics is thereby manufactured. can do.
In addition, since the manufacturing process can be performed at a high temperature of 500 ° C. or higher, it is possible to eliminate restrictions on handling during manufacturing.

Furthermore, in the present embodiment, the insulating layer 16 is formed, and further, the stress relaxation layer 50 is made of oxide or nitride, thereby further improving the insulating property (voltage resistance characteristic) of the substrate 10. Can do. Moreover, as described above, the substrate 10 is excellent in heat resistance. Thereby, the thin film solar cell 30 excellent in durability and a shelf life can be obtained. For this reason, durability and a shelf life are excellent also about a solar cell submodule and a thin film solar cell module.
Furthermore, in the present embodiment, when the stress relaxation layer 50 includes an alkali metal, the stress relaxation layer 50 functions as an alkali metal supply source. Thereby, during formation of the photoelectric conversion layer 34, an alkali metal can be diffused in the photoelectric conversion layer 34, and a photoelectric conversion efficiency can be improved. In this case, although the film-forming process of the photoelectric conversion layer is required to have a higher temperature, the substrate 10 has high-temperature resistance as described above, and therefore, an alkali metal can be diffused into the photoelectric conversion layer.

  Moreover, in this embodiment, the board | substrate 10 is manufactured by a roll-to-roll system, and has flexibility. For this reason, the photoelectric conversion element 40 and the thin film solar cell 30 can also be manufactured by a roll-to-roll method, for example, conveying the board | substrate 10 to the longitudinal direction L. Thus, since the thin film solar cell 30 can be manufactured by an inexpensive roll-to-roll method, the manufacturing cost of the thin film solar cell 30 can be reduced. Thereby, the cost of a solar cell submodule or a thin film solar cell module can be reduced.

  The present invention is basically as described above. As mentioned above, although the manufacturing method of the photoelectric conversion element of this invention, the thin film solar cell, and the photoelectric conversion element was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, it is various improvement. Of course, changes may be made.

Hereinafter, experimental examples of the photoelectric conversion element of the present invention will be specifically described.
In this experimental example, Experimental Examples 1 to 7 shown below were created, and the difference in effect due to the layer configuration was examined.

(Experimental example 1)
Cold rolling method using commercially available ferritic stainless steel material (material SUS430, coefficient of thermal expansion 10.5 × 10 ⁻⁶ / ° C.) and high purity aluminum material (hereinafter referred to as Al material) having a purity of 4N By applying pressure bonding and reducing the thickness, a three-layer clad material having a ferritic stainless steel material thickness of 50 μm and an Al material thickness of 30 μm was formed to obtain a metal substrate. The configuration of this metal substrate is Al material (30 μm) / ferritic stainless steel material (50 μm) / Al material (30 μm).
With respect to this metal substrate, the stainless steel surface and end surface of the metal substrate were covered with a masking film. Then, after ultrasonic cleaning with ethanol, electropolishing with acetic acid + perchloric acid solution, electrolysis with constant voltage of 40 V in an 80 g / L oxalic acid solution, the thickness of the insulating layer is 10 μm. An anodized film was formed on the surface of the Al material. The thickness of the Al material after the anodizing treatment was 15 μm. The substrate with an insulating layer having the structure of anodized film (10 μm) / Al material (15 μm) / ferritic stainless steel material (50 μm) / Al material (15 μm) / anodized film (10 μm) was obtained by the above process.
Next, a blue plate glass (soda lime glass, SLG) having a thermal expansion coefficient of 7 to 8 × 10 ⁻⁶ / ° C. is formed to a thickness of 200 nm by RF sputtering as a stress relaxation layer on one surface of the substrate with an insulating layer. A film was formed. This was designated as Experimental Example 1.

(Experimental example 2)
Using the same metal substrate with an insulating layer as in Experimental Example 1, and further using as a stress relaxation layer on one side of the metal substrate with an insulating layer, alumina having a thermal expansion coefficient of 8.4 × 10 ⁻⁶ / ° C. by reactive sputtering. Al ₂ O ₃ ) was deposited to a thickness of 200 nm. This was designated as experimental example 2.

(Experimental example 3)
The same metal substrate with an insulating layer as in Experimental Example 1 was used, and two stress relaxation layers were formed on one side of the metal substrate with an insulating layer as follows. First, as a first layer of a stress relaxation layer, aluminum nitride (AlN) having a thermal expansion coefficient of 5.7 × 10 ⁻⁶ / ° C. is formed to a thickness of 100 nm on a metal substrate with an insulating layer by reactive sputtering. A film was formed. Further, a blue plate glass having a thermal expansion coefficient of 7 to 8 × 10 ⁻⁶ / ° C. was formed to a thickness of 100 nm as a second layer of the stress relaxation layer on the first layer by RF sputtering. . This was designated as Experimental Example 3.

(Experimental example 4)
The same metal substrate with an insulating layer as in Experimental Example 1 was used, and two stress relaxation layers were formed on one side of the metal substrate with an insulating layer as follows. First, blue plate glass having a thermal expansion coefficient of 7 to 8 × 10 ⁻⁶ / ° C. was formed to a thickness of 100 nm on a metal substrate with an insulating layer as a first layer of a stress relaxation layer by RF sputtering. Further, on the first layer, titanium oxide (TiO ₂ ) having a thermal expansion coefficient of 9.0 × 10 ⁻⁶ / ° C. is formed to a thickness of 100 nm by reactive sputtering as a second layer of the stress relaxation layer. A film was formed. This was designated as Experimental Example 4.

(Experimental example 5)
The thickness of the Kovar alloy material is obtained by pressure bonding and reducing the thickness of a commercially available Kovar alloy material (thermal expansion coefficient 5 × 10 ⁻⁶ / ° C.) and a high purity Al material having a purity of 4N by cold rolling. A three-layer clad material having a thickness of 50 μm and an Al material thickness of 30 μm was prepared and used as a metal substrate. The structure of the metal substrate is Al base material (30 μm) / Kovar alloy material (50 μm) / Al base material (30 μm).
This metal substrate was coated with a masking film on the Kovar alloy surface and end surface of the metal substrate, ultrasonically cleaned with ethanol, electropolished with an acetic acid + perchloric acid solution, and then 40 V in an 80 g / L oxalic acid solution. By performing constant voltage electrolysis, an anodic oxide film having a thickness of 10 μm was formed on the surface of the Al material as an insulating layer. The thickness of the Al material after the anodizing treatment was 15 μm. The substrate with an insulating layer having the structure of anodized film (10 μm) / Al material (15 μm) / Kovar alloy material (50 μm) / Al material (15 μm) / anodized film (10 μm) was obtained by the above process. Further, a blue plate glass having a thermal expansion coefficient of 7 to 8 × 10 ⁻⁶ / ° C. was formed in a thickness of 200 nm on one side of the metal substrate with an insulating layer as a stress relaxation layer by RF sputtering. This was designated as Experimental Example 5.

(Experimental example 6)
Using a commercially available austenitic stainless steel material (material SUS304, coefficient of thermal expansion of 17 × 10 ⁻⁶ / ° C.) and a high purity aluminum material with a purity of 4N, press bonding and reducing the thickness by cold rolling. Thus, a three-layer clad material having an austenitic stainless steel material thickness of 50 μm and an Al material thickness of 30 μm was formed to obtain a metal substrate. The structure of this metal substrate is Al material (30 μm) / austenite stainless steel material (50 μm) / Al material (30 μm).
With respect to this metal substrate, the stainless steel surface and end surface of the metal substrate were covered with a masking film. Then, after ultrasonic cleaning with ethanol, electropolishing with acetic acid + perchloric acid solution, electrolysis with constant voltage of 40 V in 80 g / L oxalic acid solution, an anodic oxide film having a thickness of 10 μm is formed as an insulating layer. It formed on the surface of Al material. The thickness of the Al base material after the anodizing treatment was 15 μm. The substrate with an insulating layer having the structure of anodic oxide film (10 μm) / Al material (15 μm) / austenitic stainless steel material (50 μm) / Al material (15 μm) / anodized film (10 μm) was obtained by the above steps.
Furthermore, a blue plate glass having a thermal expansion coefficient of 7 to 8 × 10 ⁻⁶ / ° C. was formed as a stress relaxation layer on one side of the metal substrate with an insulating layer to a thickness of 200 nm by RF sputtering. This was designated as Experimental Example 6.

(Experimental example 7)
The same metal substrate with an insulating layer as in Experimental Example 1 is used, and no stress relaxation layer is formed thereon. This was designated as Experimental Example 7.

  Next, with respect to Experimental Examples 1 to 7, the sample was left as it was (no heating), was heat-treated at 500 ° C. for 1 hour in a vacuum heating furnace, and was heat-treated at 580 ° C. for 0.5 hour in a vacuum heating furnace. The insulation characteristics were compared with those in the state.

In this experimental example, when measuring the insulation characteristics, in Experimental Examples 1 to 6, on the stress relaxation layer, in Experimental Example 7 on the anodic oxide film, and as an electrode by mask vapor deposition, the diameter is 3.5 mm and the thickness is A 0.2 μm Au electrode was formed. Then, a voltage of 200 V was applied between the metal substrate and the Au electrode, with the Au electrode serving as a negative electrode, and the leakage current flowing between the metal substrate and the Au electrode when the voltage was applied was measured. Here, the value obtained by dividing the detected leakage current by the Au electrode area (9.6 mm ² ) was defined as the leakage current density. This leakage current density was used for the evaluation of the insulation characteristics.
Table 1 below shows the results (leakage current density) of each insulation characteristic measurement for Experimental Examples 1 to 7.

As shown in Table 1 below, Experimental Examples 1 to 5 are provided with a stress relaxation layer, and compared with Experimental Example 7, the leakage current density does not change even when heat treatment is performed at a higher temperature at 580 ° C. It was.
Further, Experimental Example 6 was provided with a stress relaxation layer, and compared with Experimental Example 7, the change in leakage current density was small even when heat treatment was performed at a higher temperature of 580 ° C.
On the other hand, in Experimental Example 7, no stress relaxation layer was provided, and the leakage current density increased when heat treatment was performed at 580 ° C.

In this experimental example, Experimental Examples 10 to 30 shown below were prepared, and the difference in effect due to the difference in thermal expansion coefficient between the metal substrate and the photoelectric conversion layer was examined.
As shown in Table 2 below, Experimental Example 10 to Experimental Example 30 are obtained by forming a back electrode and a photoelectric conversion layer (semiconductor layer) for the above-described metal substrates with an insulating layer of Experimental Examples 1 to 7, respectively.
For each of Experimental Examples 10 to 30, the surface state of the photoelectric conversion layer (semiconductor layer) surface was evaluated.

In Experimental Examples 10 to 30, the metal substrate with an insulating layer of Experimental Examples 1 to 7 described above was used, and the Mo film was formed to a thickness of 800 nm as a back electrode on the stress relaxation layer or the anodic oxide film. It formed by the sputtering method.
Next, a photoelectric conversion layer (semiconductor layer) was formed on the back electrode at a substrate temperature of 580 ° C. As the photoelectric conversion layer (semiconductor layer), one of GaAs, Cu (In _0.7 Ga _0.3 ) Se ₂ and CdTe was formed.
GaAs and Cu (In _0.7 Ga _0.3 ) Se ₂ were formed to a thickness of 2 μm by an evaporation method using a K cell (knudsen-Cell) as an evaporation source. On the other hand, CdTe was formed to a thickness of 5 μm using a proximity sublimation method.

In Table 2 below, the substrate used in each of Experimental Examples 10 to 30, the configuration of the stress relaxation layer, the composition of the photoelectric conversion layer, the difference in thermal expansion coefficient between the substrate, the stress relaxation layer, and the photoelectric conversion layer, and the photoelectric The evaluation of the surface state of the conversion layer surface is shown.
In the evaluation of the surface state of the surface of the photoelectric conversion layer, the surface of the photoelectric conversion layer after film formation was observed with an optical microscope, and the case where partial peeling or cracks occurred was evaluated as x.
In addition, an Au film having a diameter of 3.5 mm and a thickness of 0.2 μm is provided as an upper electrode on the photoelectric conversion layer by a mask vapor deposition method, and a resistance value between the upper electrode and the back electrode is measured, and a microcrack is measured. Or the presence or absence of the leakage current by the micro crack which cannot be confirmed with an optical microscope was confirmed. A case where partial peeling or cracking was not observed in the observation with the above-mentioned optical microscope and continuity was confirmed was evaluated as Δ.
Moreover, the partial peeling or the crack was not observed by observation with the above-mentioned optical microscope, and it was set as (circle) that there is no leakage current by the above-mentioned measurement of leakage current.

Experimental Examples 10 to 24 using Experimental Examples 1 to 5 use a base material that matches the thermal expansion coefficient of the photoelectric conversion layer (semiconductor layer), and between the anodized film and the photoelectric conversion layer (semiconductor layer), A high-quality photoelectric conversion in which partial peeling or cracking does not occur when a photoelectric conversion layer (semiconductor layer) is formed at a high temperature of 580 ° C. by forming a material having a thermal expansion coefficient intermediate between the two as a stress relaxation layer. A layer (semiconductor layer) could be obtained.
In Experimental Examples 25 to 27, although the stress relaxation layer is provided, the difference in the thermal expansion coefficient between the base material and the photoelectric conversion layer is large, but the change in the leakage current density when heat-treated at 580 ° C. is not so large. When the photoelectric conversion layer (semiconductor layer) was formed at a high temperature of 580 ° C., partial peeling or cracking occurred.
On the other hand, in Experimental Examples 28 to 30, since there is no stress relaxation layer, when a photoelectric conversion layer (semiconductor layer) is formed at a high temperature of 580 ° C., partial peeling or cracking occurs, and a high-quality photoelectric conversion layer (semiconductor layer). Could not get.

In this experimental example, Experimental Examples 40 to 46 shown below were prepared, and the adhesion between the metal substrate and the back electrode was examined.
Experimental Example 40 to Experimental Example 46, as shown in Table 3 below, use the metal substrate with an insulating layer of Experimental Examples 1 to 7 described above, and each of the Mo film as a back electrode on the stress relaxation layer or the anodic oxide film. Is formed by DC sputtering to a thickness of 600 nm.
The film formation conditions were such that the film formation gas pressure was 0.5 Pa, the sputtering gas was Ar gas, and the substrate temperature was room temperature.

  The evaluation of the adhesion of the back electrode was carried out for each of Experimental Examples 40 to 46 as they were (without heating) and after heat treatment at 550 ° C. for 0.5 hours in a vacuum heating furnace (heating at 550 ° C. An adhesion test by a cross-cut method was performed for each of the latter and the ones according to JIS standard K5600.

Specifically, the evaluation of the adhesion of the back electrode was performed by setting the interval between cuts of the cross-cut method to 1 mm, and depending on the peeling condition of the 25 grids and the cut intersection after the adhesion (adhesion) test. evaluated.
For scoring for adhesion evaluation, the number of peeled masses was evaluated as a percentage, and ranked from no peel (100%) to full peel (0%). The evaluation results of the adhesion of the back electrode described above are shown in Table 3 below.

In all of Experimental Examples 40 to 46, those in the same state (without heating) had good adhesion because no stress due to the difference in thermal expansion coefficient was applied.
Among the experimental examples 40 to 46, the experimental examples 40 to 44 did not peel even when heat-treated at 550 ° C. and had good adhesion.
On the other hand, in Experimental Example 45, when heat-treated at 550 ° C., it is estimated that the adhesiveness was lowered due to a strain that seems to be a stress caused by a difference in thermal expansion between the substrate and the Mo film.
Further, in Experimental Example 46, since the Mo film is formed immediately above the anodic oxide film, the contact area is smaller than that including the stress relaxation layer, and the interface between the metal and the oxide is different. It is presumed that the adhesiveness was lowered when heat treatment was performed at 550 ° C.

In this experimental example, Experimental Examples 50 to 56 shown below were prepared, and the adhesion of the photoelectric conversion layer (CIGS layer) was examined.
As shown in Table 4 below, Experimental Example 50 to Experimental Example 56 are a back electrode and a photoelectric conversion layer (on the stress relaxation layer or the anodic oxide film, respectively) on the metal substrate with an insulating layer of Experimental Examples 1 to 7 described above. CIGS layer) is formed.
As the back electrode, a Mo film was formed to a thickness of 600 nm by DC sputtering. The film forming conditions are the same film forming conditions as those in the third embodiment, and a detailed description thereof will be omitted.
In addition, the photoelectric conversion layer (CIGS layer) was made of 2 μm of Cu (In _0.7 Ga _0.3 ) Se ₂ on the back electrode in the same manner as in Example 2 except that the substrate temperature was 520 ° C. The film was formed to a thickness of.

  The evaluation of the adhesion of the photoelectric conversion layer (CIGS layer) was carried out by conducting an adhesion test in accordance with JIS standard K5600 in the same manner as in Example 3 above, to evaluate the adhesion. The scoring for evaluation of adhesion was also the same as in Example 3 above. For this reason, detailed description of the evaluation of the adhesion of the photoelectric conversion layer (CIGS layer) is omitted. Table 4 below shows the evaluation results of the adhesion of the photoelectric conversion layer (CIGS layer).

Among Experimental Examples 50 to 56, Experimental Examples 50 to 53 had good adhesion of the photoelectric conversion layer (CIGS layer).
On the other hand, the adhesiveness was good in Example 3 described above (see Experimental Example 44 of Example 3), but Experimental Example 54 in which a decrease in adhesiveness was newly observed was the base material of the metal substrate with an insulating layer. It is presumed that the stress relaxation layer could not alleviate the thermal expansion coefficient difference between (Kovar) and the photoelectric conversion layer (CIGS layer).
In addition, with respect to Experimental Example 55, in addition to the decrease in adhesion of Experimental Example 45 in Example 3 described above, the difference in thermal expansion coefficient between the photoelectric conversion layer (CIGS layer) and the base material (SUS304) is also combined, resulting in more adhesion. Is estimated to be low.

  Furthermore, also in Experimental Example 56, it is estimated that the adhesiveness of the photoelectric conversion layer (CIGS layer) is low because the adhesiveness of Experimental Example 46 of Example 3 described above is low. However, since the difference in thermal expansion coefficient between the base material (SUS430) of the metal substrate with an insulating layer and the photoelectric conversion layer (CIGS layer) is smaller than that in Experimental Example 55, the degree of decrease in adhesion compared to Experimental Example 55. Is estimated to be small.

10 Substrate 12 Metal base 14 Aluminum base (Al base)
16 Insulating Layer 30 Thin Film Solar Cell 32 Back Electrode 34 Photoelectric Conversion Layer 36 Buffer Layer 38 Transparent Electrode 40 Photoelectric Conversion Element 42 First Conductive Member 44 Second Conductive Member 50 Stress Relieving Layer

Claims (24)

A metal substrate in which at least one metal base material and an Al base material are laminated and integrated, and a substrate with an insulating layer including an electrical insulating layer formed on a surface of the Al base material of the metal substrate;
At least one stress relaxation layer formed on the electrical insulating layer;
A lower electrode formed on the stress relaxation layer;
A photoelectric conversion layer formed on the lower electrode and composed of a compound semiconductor layer;
An upper electrode formed on the photoelectric conversion layer,
The photoelectric conversion element, wherein the electrical insulating layer is an anodized film of aluminum.   The photoelectric conversion element according to claim 1, wherein the compound semiconductor is at least one compound semiconductor having a chalcopyrite structure.   The photoelectric conversion device according to claim 2, wherein the compound semiconductor is at least one compound semiconductor composed of a group Ib element, a group IIIb element, and a group VIb element. The Ib group element is at least one selected from the group consisting of Cu and Ag,
The IIIb group element is at least one selected from the group consisting of Al, Ga and In,
The photoelectric conversion element according to claim 3, wherein the group VIb element is at least one selected from the group consisting of S, Se, and Te.   The photoelectric conversion element according to any one of claims 1 to 4, wherein the stress relaxation layer has a thermal expansion coefficient smaller than that of the photoelectric conversion layer and larger than that of the insulating layer. .   The photoelectric conversion element according to claim 1, wherein the stress relaxation layer is made of an oxide.   The photoelectric conversion element according to claim 1, wherein the stress relaxation layer has a thickness of 10 nm to 400 nm.   The photoelectric conversion element according to claim 7, wherein the stress relaxation layer has a thickness of 50 nm to 200 nm. The photoelectric conversion layer according to any one of claims 1 to 8, wherein the photoelectric conversion layer is divided into a plurality of elements by a plurality of open grooves, and the plurality of elements are electrically connected in series. Conversion element.   The photoelectric conversion element according to claim 1, wherein the stress relaxation layer contains an alkali metal.   The photoelectric conversion element according to claim 10, wherein the stress relaxation layer is made of a compound containing silicon oxide as a main component and containing sodium oxide.   The said stress relaxation layer is a 2 layer structure, The thermal expansion coefficient of the 1st stress relaxation layer by the side of the said board | substrate with an insulating layer is smaller than the 2nd stress relaxation layer on it. The photoelectric conversion element of Claim 1. The stress relaxation layer has a two-layer structure, and when the photoelectric conversion layer is composed of a CIGS-based semiconductor compound, the first stress relaxation layer on the substrate side with an insulating layer includes ZrN, AlN, BN, Al consists of _{2 O} 3 or ZrO _2,, the second stress relieving layer thereon, any one of constituted claims 1-12 with a compound of silicon oxide as a main component, and containing sodium oxide The photoelectric conversion element as described in 2.   The photoelectric conversion element according to claim 1, wherein the metal substrate is a laminated plate in which a metal base and an Al base are integrated by pressure bonding.   The photoelectric conversion element according to claim 14, wherein the metal base material is a steel material, an alloy steel material, a Ti foil, or a two-layer base material of a Ti foil and a steel material.   The photoelectric conversion element according to claim 15, wherein the alloy steel material is made of carbon steel or ferritic stainless steel. The photoelectric conversion element according to claim 1, wherein a difference in thermal expansion coefficient between the metal substrate and the photoelectric conversion layer is less than 3 × 10 ⁻⁶ / ° C. The photoelectric conversion element according to claim 17, wherein a difference in thermal expansion coefficient between the metal substrate and the photoelectric conversion layer is less than 1 × 10 ⁻⁶ / ° C.   The metal substrate is made of a laminated plate in which an alloy steel material made of carbon steel or ferritic stainless steel and an Al base material are integrated by pressure bonding, and the lower electrode is made of Mo, The photoelectric conversion element according to claim 1, wherein the photoelectric conversion layer is a layer mainly composed of at least one compound semiconductor composed of a group Ib element, a group IIIb element, and a group VIb element.   The photoelectric conversion element according to any one of claims 1 to 15, 17, and 18, wherein the metal substrate is made of Kovar, and the photoelectric conversion layer is made of a compound semiconductor whose main component is CdTe.   The photoelectric conversion element according to claim 1, wherein the anodic oxide film has a porous structure.   A thin film solar cell comprising the photoelectric conversion device according to claim 1. Forming a metal substrate by integrating at least one layer of a metal base material and an Al base material; and
Anodizing the Al base of the metal substrate, forming an electrical insulating layer on the Al base, and obtaining a substrate with an insulating layer;
Forming a stress relaxation layer on the electrical insulating layer;
Forming a lower electrode on the stress relaxation layer;
Forming a photoelectric conversion layer on the lower electrode at a film forming temperature of 500 ° C. or higher;
And a step of forming an upper electrode on the photoelectric conversion layer. The metal substrate is a laminated plate in which a metal substrate and an Al substrate are laminated and integrated,
The method for producing a photoelectric conversion element according to claim 23, wherein the step of obtaining the substrate with an insulating layer is a step of anodizing the Al base material to form an anodized film on the surface of the Al base material.